FR3072412A1 - DETECTION OF BLOCKED PIPING - Google Patents

Abstract

The tight spots in a drill string in a petroleum well are identified by comparing an average load-to-hook motion at a wide range to an average movement of the hook load. At a small interval, comparing a mean of movement of the depth of the trench at a large interval and a mean of movement of the depth of the trench at a small interval, and DBSCANing the tight places to identify a vertex Completely blocked.

Description

Detection of a blocked pipeline

Background Drilling a borehole to form a well includes the use of a drill string to which a drill bit is attached. The drill string can be blocked in the borehole for a variety of reasons. Continuing to use drilling equipment when the drilling rig is blocked can damage the drilling rig or drilling equipment. Detecting that a drill string is stuck in a borehole is a challenge.

Brief Description of the Drawings [0002] Figure 1 is a block diagram of a land drilling system.

[0003] FIG. 2 is a graph showing the hook load over time in a blocked pipe situation.

[0004] FIG. 3 shows two graphs illustrating the means of displacement of a hook load and the means of movement of the depth of the drill bit over time.

[0005] FIG. 4 is a flow diagram of a technique for detecting a blocked pipe.

[0006] FIG. 5 is a flow diagram of an environment.

Detailed Description [0007] Even if this disclosure describes a land drilling system, it will be understood that the equipment and techniques described here are applicable to seabed systems, multilateral wells, all types of drilling systems, all types of platforms, measurements during drilling ("MWD") / logging during drilling ("LWD"), wired drill train environments, wound tube environments (wired or not), cable work environments, and similar environments.

An embodiment of a drilling operation system (or "drilling system") 5, illustrated in FIG. 1, comprises a drilling platform 10 at a surface 12, supporting a drill string 14. In one embodiment, the drill string 14 is an assembly of sections of drill pipe which are connected end-to-end. butted across a working platform 16. In alternative embodiments, the drill string includes coiled tubing rather than individual drill pipes. In one embodiment, a drill bit 18 is coupled to the lower end of a drill string 14, and through drilling operations, the drill bit 18 digs a borehole 20 through the earth formations 22 and 24.

In one or more embodiments, the drilling system 5 comprises a drill string 26 for raising and lowering the drill string 14 in the borehole 20. In one or more embodiments, the drill string 26 is wound on a winch or a lifting mechanism 28. In one or more embodiments, the drill string 26 passes from the winch or of the lifting mechanism 28 to a fixed block 30. In one or more embodiments, the drill string passes from the fixed block 30 to a movable block 32 and back to the fixed block 30 and on an anchor 34. In one or more embodiments, a hook 36 couples the mobile block 32 to the drill train 14. In one or more embodiments, the fixed block 30 and the movable block 32 act as a block block to give a mechanical advantage when lifting or lowering the drill string 14. In one or more embodiments, the drilling rig 26 comp makes a fast line 38 which extends from the lifting mechanism 28 towards a fixed block 30 and a limit 40 which extends from the fixed block 30 towards the anchor 34. In one or more embodiments, a supply reel 42 stores additional drill string 26 which can be used when the drill string 26 has been used for a period of time and considered worn.

In one or more embodiments, a hook load sensor 44 emits signals representative of the load imposed on the drill string 14 on the hook 36. In one or more embodiments, the sensor of the hook load 44 is coupled to a limit 40 for measuring the tension in the drill string 26. In one embodiment, the signals from the hook load sensor 44 are coupled to a processor 46 by a cable 48. The processor 46 processes the signals from the hook load sensor 44 in order to determine the "hook load" which represents the weight of the drill string 14 suspended from the hook 36.

In one or more embodiments, a bit depth sensor 50 emits signals representative of the bit depth 18 in the borehole 20. In one or more embodiments, the depth sensor drill bit is an optical sensor which measures the rotation of the winch or of the lifting mechanism 28. In one embodiment, the signals coming from the depth sensor 50 are coupled to the processor 46 by a cable 52. The processor 46 processes the signals coming from of the bit depth sensor 44 in order to determine the "bit depth", which represents the distance along the borehole 20 from the surface 12 to the bit 18.

The drill string 14 can remain blocked in the borehole 20 for a variety of reasons, including collapsing of the borehole 20, differential wedging in which the pressure exerted by the drilling fluids exceeds the pressures of the formation, which sticks the drill string 14 to the wall of the borehole 20, expanding the borehole 20, etc. Once the drill string 14 is blocked, pulling the train 14 with pressure exceeding a safe limit can damage the drill string 14 or other equipment in the drilling system 5.

This phenomenon is illustrated in FIG. 2, which shows a hook load on the vertical axis and time on the horizontal axis. As can be seen, the hook load is relatively stable, indicating normal triggering operation 202 when it begins to increase dramatically. At point 204, a person responsible for controlling the pulling force on the drill string 26 and therefore on the drill string 14 (ie, a "driller") realizes that the hook load has increased and reduces the pulling force. The hook load then drops back down to normal at approximately point 206. The driller uses the time between points 206 and 208 to decide what to do next, perhaps by analyzing the data or talking to other drillers . Then, at point 208, the driller decides to exert greater traction than that exerted previously and begins to increase the traction up to point 210, where the drill string 14 or other parts of the drilling system 5 are damaged. .

In one or more embodiments, the tight spots in the movement of the drill string 14 in the borehole 20 are identified by comparing an average movement of the hook load over a large interval to an average of movement of a hook load over a small interval and comparing an average movement of a bit depth over a large interval to an average movement of the bit depth over a small interval. In one or more embodiments, the tight spots are then DBSCANnes (shown below) to identify a total blocking event.

In one or more embodiments, the processor 46 receives periodic signals from the hook load sensor 44. In one or more embodiments, each time the processor 46 receives a signal from the load sensor the hook load 44, it calculates the means of movement of these signals by calculating the average of the values coming from the sensors over periods of time. In one or more embodiments, the processor calculates the average of movement for each Pe periodic signal coming from the hook load sensor 44, where P 2.

In one or more embodiments, the processor 46 calculates a large interval of the average movement of the hook load by calculating an average of the signals received from the hook load sensor 44 over a large time interval:

_ ° _ (signal f rom hookload sensor 44) movingavgLHKLD = ^{c to HKLD} ---------------------- (1) ⁿ HKLD where:

te = current time, to = offset,

Lhkld ⁼ duration of the large hook load interval,

Nhkld ⁼ the number of samples taken during the long hook load interval.

For example, if to is zero and Lhkld is 4 minutes (or 240 seconds), processor 46 will add the signals from the load sensor to hook 44 for the previous 4 minutes starting at the current time and divided by Nhkld · If t ₀ is 30 seconds and Lhkld is 4 minutes, the processor 46 will add the signals coming from the load sensor to the hook 44 for the previous 4 minutes starting at 30 seconds before the current time and divided by Nhkld · [0018] In one or more embodiments, the processor 46 calculates a small interval of the average motion of the hook load by calculating an average of the signals received from the sensor of the hook load 44 over a small time interval:

y _t ^{c to} (signal from hookload sensor 44) moving avg S HKLD = —---------------------- (2) ^m hkld where:

L = current weather,

L = offset,

Shkld ⁼ time duration of the small hook charge interval,

Mhkld = the number of samples taken during the small hook load interval.

For example, if to is zero and Shkld is 15 seconds, processor 46 will add the signals from the load sensor to hook 44 for the previous 15 seconds starting at the current time and divided by Mhkld- If t _o is 30 seconds and Shkld is 15 seconds, the processor 46 will add the signals coming from the load sensor to the hook 44 for the preceding 15 seconds starting 30 5 seconds before the current time and divided by Mhkld · [0020] In one or more modes of realization, Lhkld> Shkld · In one or more embodiments, Lhkld "(ie, much larger than) Shkld · In one or more embodiments," much greater than "means at least 50 times. In one or more embodiments, "much larger than" means at least 16 times. In one or more embodiments, "much larger than" means at least 8 times.

In one or more embodiments, the processor 46 receives periodic signals from the bit depth sensor 50. In one or more embodiments, each time the processor 46 receives a signal from the sensor the depth of the drill bit 50, it calculates the means of movement of these signals by calculating the average of the values coming from the 15 sensors over periods of time. In one or more embodiments, the processor calculates the motion averages for each periodic signal Qe coming from the bit depth sensor 50, where Q S 2.

In one or more embodiments, the processor 46 calculates a large interval of the average movement of the depth of the drill bit (or the depth of the BLK POS blocking) by calculating an average of the signals coming from the sensor of the drill bit depth 50 over a large time interval:

or:

L = current time, offset,

Lblk_pos = duration of the large interval of the drill bit depth,

Nblk pos ⁼ number of samples taken during the long interval of the drill bit depth.

For example, if to is zero and Lblk_pos is 4 minutes (or 240 seconds), processor 46 will add the signals from the bit depth sensor 50 for the previous 4 minutes starting at the current time and divided by N _B lk_pos- If t ₀ is 30 seconds and Lblk pos is 4 minutes, processor 46 will add the signals from the bit depth sensor 50 for the previous 4 minutes starting at 30 seconds before the current time and divided by Nblk_pos · [ In one or more embodiments, the processor 46 calculates a small interval of the average movement of the bit depth (or the depth of the BLK POS blocking) by calculating an average of the signals from the depth sensor. drill bit 50 over a small time interval:

movingavgLBLKPOS = ^to (signal from hookload sensor 44) c-to-SBUÇPOS _____________________________

MbLK_POS (4) where:

T = current time, to = offset,

Sblk pos = duration of the small interval of the bit depth,

Mblkpos = number of samples taken during the small interval of the bit depth.

For example, if t ₀ is zero and Sblk pos is 15 seconds, processor 46 will add the signals from the bit depth sensor 50 for the previous 15 seconds starting at the current time and divided by Mblk pos · Si t ₀ is 30 seconds and Sblk pos is 15 seconds, processor 46 will add the signals from the bit depth sensor 50 for the previous 15 seconds starting before 30 seconds before the current time and divided by Mblk_pos · In a or more embodiments, the L _B lk_pos> Sblk pos · In one or more embodiments, the L _B lk_pos "(ie, is much larger than) Sblk.pos · In one or more embodiments, "much larger than" means at least 50 times. In one or more embodiments, "much larger than" means at least 16 times. In one or more embodiments, "much larger than" means at least 8 times.

In one or more embodiments, the Lhkld ⁼ L _B lkpos · In one or more embodiments, the Lhkld î Lblk_pos · In one or more embodiments, Shkld = Sblk pos · In one or several embodiments, Shkld # Sblk pos · In one or more embodiments, Nhkld = N _B lk pos · In one or more embodiments, Nhkld t Nblk pos · [0030] In one or more embodiments realization, Mhkt.d = M _B lk pos · In one or more embodiments, Mhkld # Mblk pos · [0031] FIG. 3 illustrates examples of motion averages. Fig. 3 illustrates two sets of axes. The first set of axes in the figure is for the averages of the movement of the hook load. In one or more embodiments, the units of the horizontal axis for the first set of axes is time. In one or more embodiments, the vertical axis for the first set of axes is a logarithmic scale having units of thousands of pounds of force ("kips"). The second set of axes at the bottom of the figure represents the average of the movement of the depth of the drill bit. In one or more embodiments, the units of the horizontal axis for the second set of axes is time. In one or more embodiments, the horizontal axis for the second set of axes is aligned with the horizontal axis for the first set of axes. In one or more embodiments, the vertical axis for the first set of axes has units in feet.

In one or more embodiments, the first set of axes illustrated in FIG. 3 illustrates an average movement of the hook load over a large interval 302 and an average movement of the hook load over a small interval 304. In one or more embodiments, the second set of axes of FIG. 3 illustrates an average movement of the depth of the drill bit over a large interval 306 and an average movement of the depth of the drill bit over a small interval 308. It should be noted that in both cases, in one or more embodiments, the average of long interval movement (ie, 302 and 306) is smoother than the average of short interval movement (i.e., 304 and 308). The reason is that, in one or more embodiments, the long interval movement averages capture the larger trends, filtering out some of the instantaneous trends that are evident in the short interval movement means. In one or more embodiments, the technique described here takes advantage of the differences between long interval movement averages and short interval movement averages to identify "tight spot" events. In one or more embodiments, a tight location event occurs when the absolute value of the difference between the average motion of the hook at long interval 302 and the mean of motion of the hook at short interval 304, AHKLD, is greater than the hook load threshold, THhkld, and the absolute value of the difference between the average movement of the bit depth at long intervals 306 and the average movement of depth of bits at short intervals 308, ABLKPOS, is less than a drill bit depth threshold, THblk:

AHKLD> THhkld AND ABLKPOS <TH _BLK (5) where:

AHKLD = \ moving_avg_L_HKLD - moving_avg_S_HKLD \ (6)

ABLKPOS = \ moving_avg_L_BLK_POS - moving_avg_S_BLK_POS \ (7) [0033] Such a determination indicates that the hook load increases when the drill bit does not move as much as expected, which is a symptom of a tight place.

In the example illustrated in FIG. 3, this state is encountered on the intervals Ii and I2. When a reading from the hook load sensor 44 and / or the bit depth sensor 50 is received and equation (5) is satisfied, the processor retrieves the bit depth and stores it in a tight location file.

In one or more embodiments, the processor analyzes the files of tight places in order to determine whether they are grouped in depth. A grouping of files of tight locations at a given depth indicates that the drill string 14 is blocked at this depth.

In one or more embodiments, the processor performs a DBSCAN of the depths recorded in the files of the tight places. In one or more embodiments, the DBSCAN identifies groupings of tight locations within a depth range (ε) of a complete blocking depth associated with one of the tight location files. In one or more embodiments, if the number of such points is greater than the threshold M, then the processor 46 displays a complete blocking event on a screen. In one or more embodiments, the driller can then stop operations and avoid the events illustrated in dotted lines in the

Fig. 3 which could lead to breakage of the drilling train 14 or other equipment of the drilling system 5. In one or more embodiments, ε <= 10 feet and M> = 30 points. In one or more embodiments, ε <= 50 feet and M> = 60 points. In one or more embodiments, ε <= 100 feet and M> = 300 points.

In one or more embodiments, as shown in FIG. 4, the blocked pipe detection process begins (block 402) and enters a loop. In one or more embodiments, the processor 46 recovers a hook load (HLKD) from the hook load sensor 44 and the blocking position (BLK POS) or bit depth from the bit depth sensor 50 (block 404). In one or more embodiments, the processor 46 calculates the motion averages with equations (1) to (4) (block 406). In one or more embodiments, the processor 46 calculates AHKLD and ABLKPOS with equations (6) and (7) (block 408). In one or more embodiments, the processor then applies the condition of equation (5) (block 410).

In one or more embodiments, if the condition of equation (5) is satisfied (“Yes” branch of block 410), the processor “emits” a tight spot (block 412), retrieves and saves the depth of the drill bit in a “tight place” file in a file or database accessible by the DBSCAN (block 414). The DBSCAN processor the depths of the tight spot (block 416). In one or more embodiments, if a grouping is identified (“yes” branch originating from block 418), the processor 46 declares a complete blocking event and issues an alarm on a screen available to the driller. If no grouping is found (“no” branch of block 418), the processor returns to the start of the “block 404) loop.

Similarly, if the condition of equation (5) is not satisfied ("No" branch of block 410), the processor returns to the start of the loop (block 404).

Once a total blocking event has been declared, the processor 46 monitors the bit depth sensor 50 for an indication that the drill string 14 has been released and has moved out of the ranges of depth of the drill bit from any of the tight locations. The processor 46 then cancels the complete blocking event and removes the alarm from the screen.

In one embodiment, illustrated in FIG. 5, the method described above is executed by software in the form of a computer program on a non-transient computer-readable medium 505, such as a CD, a DVD, a USB key, a portable hard disk or another portable memory. In this embodiment, a processor 510, which can be the same or included in the processor 46, reads the computer program on the computer-readable medium 505 through an input / output device 515 and stores it in a memory 520 where it is prepared for execution by compilation and linking, if any, and then executed. In one embodiment, the system accepts input through an input / output device 515, such as a keyboard or numeric keypad, a mouse, a touchpad, a touch screen, etc., and transmits a output through an input / output device 515, such as a screen or a printer. In one embodiment, the system stores the results of the calculations in a memory 520 or modifies such calculations which already exist in a memory 520.

In one embodiment, the results of the calculations which are in a memory 520 are made available through a network 525 to a remote real-time operation center 530. In one embodiment, the center remote real-time operation 530 provides the calculation of results on a network 535 to assist in the planning of oil wells 540 or the drilling of oil wells 540.

In one aspect, the disclosure presents a method. The method comprises identifying the tight spots in the movements of a drilling train in an oil well by comparing an average movement of the hook load at long interval with an average movement of the load at hook short interval, by comparing an average movement of the bit depth at long intervals with an average movement of the bit depth at short intervals, and by DBSCANng the tight spots to identify a complete blocking event.

In one aspect, the disclosure presents a method. The method includes a processor determining that an average movement of a long interval hook load is greater than an average movement of a short interval hook load by a hook load threshold and that an average of movement of a bit depth at long intervals is greater than an average of movement of a bit depth at short intervals by a bit depth threshold. In response to this determination, the processor retrieves the depth of the drill bit and saves it to a folder of tight spots. The processor performs a DBSCAN of the depths recorded in the tight places folder and identifies a grouping at a complete blocking depth. In response, the processor displays a complete crash event on a screen.

The embodiments may include one or more of the following. The method may include reading the hook load from a platform. The method may include reading the depth of the drill bit from a platform. The method may include calculating the average motion of the hook load at long intervals. The method may include calculating the average motion of the hook load at a small interval. The method may include calculating the average motion of the bit depth at a large interval. The method may include calculating the average motion of the bit depth at short intervals. The method may include performing the reading and computing elements periodically. Calculation of the average motion of the hook load at long intervals may include calculating an average of the hook load over time LHKLD before the time of the most recent reading of the hook load from of the platform. The calculation of the average motion of the hook load at short intervals may include the calculation of an average of the hook load over time SHKLD <LHKLD before the time of the most recent reading of the hook load from the platform. Calculating the average bit depth movement at a large interval may include calculating an average bit depth over time LBLKPOS before the time of the most recent reading of the bit depth from of the platform. Calculating the average bit depth movement at a small interval may include calculating an average bit depth over time SBLKPOS <LBLK POS before the time of the most recent depth reading drill bit from the platform. SHKLD can be much lower than LHKLD. SBLK POS can be much lower than LBLK POS. The DBSCAN can have the following settings: a direct accessible density distance of at least 10 feet and a number of points necessary to form a grouping of at least 30. The processor can later determine that the drill string is free by based on the bit depth readings taken after the display of the complete blocking event, and therefore the deletion of the complete blocking event.

In one aspect, the disclosure describes a system. The system includes a drilling rig that contains a supply coil and an anchor. The system includes a drill string coupled to the supply coil and the anchor. The system includes a hook coupled to the drill string. The system includes a drill string suspended in a borehole, in which the drill string is suspended on the hook. The system includes a drill bit coupled to the drill string. The system includes a hook load sensor coupled to the drill string for determining a load on the hook. The system includes a drill bit depth sensor coupled to the supply spool for determining a drill bit depth. The system includes a processor for receiving inputs from the hook load sensor and the bit depth sensor to identify complete blocking events in which the drill string is blocked in a borehole.

The implementations may include one or more of the following. The processor can identify complete deadlock events by executing a method. The method may include a processor determining that an average movement of a long interval hook load is greater than an average movement of a short interval hook load by a hook load threshold and that an average movement of a bit depth at long intervals is greater than an average of movement of a bit depth at short intervals by a bit depth threshold. In response to this determination, the processor can retrieve the depth of the drill bit and save it to a tight location folder. The processor can perform a DBSCAN of the depths recorded in the files of tight places and identify a grouping at a complete blocking depth. In response, the processor may display a complete crash event on a screen.

The references in the specifications to "one or more embodiments", "an embodiment", "an embodiment", "an example of an embodiment", etc., indicate that the embodiment described may include a particular characteristic, structure, property, but that each embodiment may not necessarily include the particular characteristic, structure or property. Furthermore, such sentences do not necessarily refer to the same embodiment. In addition, when a particular property, structure or characteristic is described in relation to an embodiment, it is understood that a specialist in the field has the capacity to affect such a particular property, structure or characteristic in relation to other embodiments, whether or not explicitly described.

The embodiments include characteristics, methods or processes, which can be carried out by instructions executable by a machine contained on a support readable by a machine. A computer-readable medium includes any mechanism that provides information (i.e., stores and / or transmits) in a form accessible by a machine (eg, computer, network device, personal digital assistant , a manufacturing tool, any device with a set of one or more processors, etc.). In an exemplary embodiment, a computer-readable medium comprises a volatile and / or non-volatile non-transient medium (e.g., ROM memory, RAM memory, magnetic disk storage medium, optical storage medium , flash memory devices, etc.), transient, electrical, optical, acoustic propagated signals as well as other forms of propagated signals (e.g., carrier waves, infrared signals, digital signals, etc. ).

Such instructions are used to allow a versatile processor or a specialized processor, programmed with instructions, to carry out the methods or processes of the embodiments. Furthermore, the features or operations of the embodiments are performed by specific hardware components which include wired logic for performing the operations, or by any combination of programmed data processing components and specific hardware components. One or more embodiments include software, data processing hardware, methods of implementing a data processing system, and various processing operations, described in more detail here.

One or more figures illustrate flow diagrams of systems and apparatus for a system for monitoring a hook load, in accordance with one or more embodiments. One or more figures show flow charts illustrating the operations for monitoring a hook load, in accordance with one or more embodiments. The operations of the flowcharts are described with reference to the systems / apparatus illustrated in the flowcharts. However, it should be understood that the operations of flowcharts can be performed by embodiments of systems and apparatuses other than those described with reference to the flowcharts, and embodiments described with reference to systems / apparatuses could perform operations different from those described with reference to the organization charts.

The word "coupled" used here describes a direct connection or an indirect connection.

The above text describes one or more specific embodiments of a larger invention. The invention is also embodied in a variety of alternative embodiments and is therefore not limited by those described here. The foregoing description of an embodiment of the invention has been presented for illustrative and descriptive purposes. It is not intended that it be exhaustive or that it limit the invention to the precise form disclosed. Many modifications and variations are possible in light of the teachings given above. It is intended that the scope of this invention be limited not by the detailed description, but rather by the appended claims.

Claims (8)

What is claimed: 1. Blocked pipeline detection system comprising: a drilling rig (10) which includes a supply reel (42) and an anchor (34); a drill string (26) coupled to the supply coil and the anchor. a hook (36) coupled to the drill string. a drill string (14) suspended in a borehole (20), in which the drill string is suspended from the hook; a drill bit (18) coupled to the drill string; a hook load sensor (44) coupled to the drill string and for determining a load on the hook; a drill bit depth sensor (50) coupled to the supply spool for determining a drill bit depth; a processor (46) for receiving inputs from the hook load sensor and the bit depth sensor to identify complete blocking events in which the drill string is blocked in a borehole. 2. The blocked pipeline detection system of claim 1, wherein the processor (46) identifies complete blocking events by performing the following method: a determining processor: that an average movement of a hook load at a large interval is greater than an average movement of a hook load at a short interval by a threshold of hook load; and that an average movement of a long interval bit depth is greater than an average movement of a short interval bit depth by a bit depth threshold; and, in response: the processor retrieving the depth of the drill bit and saving it to a tight location file; the processor executing a DBSCAN of the depths recorded in the files of the tight places and identifying a grouping at a complete blocking depth, and, in response: the processor displaying a complete blocking event on a screen. 3. The blocked pipeline detection system of claim 2, in which the method also comprises: reading the hook load from a platform (10); reading the bit depth from a platform; calculating the average motion of the hook load at long intervals; calculating the average motion of the hook load at small intervals; calculating the average motion of the depth of the drill bit (18) at long intervals; and calculating the average motion of the bit depth at short intervals. 4. The blocked pipeline detection system of claim 3, in which the method also comprises: carrying out the reading and calculation elements periodically. 5. The blocked pipe detection system of claim 3, in which: calculating the average motion of the hook load at long intervals includes calculating the average of the hook load over time Lhkld before the time of the most recent reading of the hook load from the platform (10); calculating the average motion of the hook load at short intervals includes calculating an average of the hook load over time Shkld <Lhkld before the time of the most recent reading of the hook load at from the platform; calculating the average movement of the bit depth at long intervals includes calculating an average of the bit depth over time Lblk pos before the time of the most recent reading of the bit depth from of the platform; and calculating the average movement of the bit depth at short intervals includes calculating an average of the bit depth over time Sblk pos <Lblk_pos before the time of the most recent reading of the depth of the drill bit from the platform. 6. The blocked pipeline detection system of claim 5, in which: Shkld “Lhkld; and Sblk_pos ^<< Lblk_pos · 7. The blocked pipe detection system of claim 2, in which: DBSCAN has the following settings: • a direct accessible density distance of at least 10 feet; and • a number of points necessary to form a grouping of at least 30. 8. The blocked pipeline detection system of claim 2, in which the method also comprises: 5 the processor (46) can then determine that the drill string (14) is free based on the readings of the bit depth (18) made after the display of the complete blocking event, and therefore the deletion of the complete blocking event.